Time resolved photoluminescence (TRPL) and transient absorption (TA) spectroscopy reveal an
ultrafast charge transfer (CT) process, with an electron localization time constant 39+-9 ps,
between the ZnO host and the Cu dopants in Cu-doped ZnO nanowires. This CT process effectively
competes with the ZnO band edge emission, resulting in the quenching of the ZnO UV emission.
TRPL measurements show that the UV decay dynamics coincides with the buildup of the Cu-related
green emission. TA measurements probing the state-filling of the band edge and defect states
provide further support to the CT model where the bleaching dynamics concur with the TRPL
lifetimes.